1. Field of the Invention
An aspect of the present invention relates to a semiconductor integrated circuit and in particular to a reference voltage generation circuit for outputting a reference voltage.
2. Description of the Related Art
A band gap reference (BGR) circuit for outputting a given reference voltage if the ambient temperature fluctuates by using a band gap of a semiconductor is widely used with a semiconductor integrated circuit (LSI) of memory, etc. A BGR circuit that can operate on a low power supply voltage is demanded as the power supply voltage of an LSI lowers. Thus, a BGR circuit that can output a reference voltage on power supply voltage 1V or less is proposed (for example, refer to Hironori Banba et al. “A CMOS bandgap reference circuit with sub-1-v operation,” USA electronics and communications engineer association journal of solid-state circuits, vol. 34, number 5, May 1999).
The above proposed BGR circuit operates on a power supply voltage of 1V or less by lessening the threshold voltage of MOS transistors. However, the above proposed BGR circuit involves a problem of occurrence of variations in the reference voltage caused by the threshold voltage variations of PMOS transistors (p-channel MOS transistors). Especially, in an integrated circuit having a large variation in a threshold voltage of transistors, such as a ferroelectric memory, the BGR voltage varies with transistor manufacturing variations.